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THE  BULLETIN 

OF  THE 

NORTH  CAROLINA  DEPARTMENT  OF  AGRICULTURE 

RALEIGH 


MARCH,  1923 


The  Plum  Curculio  on  Peaches 
in  North  Carolina— Its  Life 

4 

History  and  Control 


Published  by  the  State  Department  of  Agriculture  for  the 

AGRICULTURAL  EXPERIMENT  STATION 

of  the 

NORTH  CAROLINA  DEPARTMENT  OF  AGRICULTURE 

and  the 

NORTH  CAROLINA  STATE  COLLEGE  OF  AGRICULTURE 

AND  ENGINEERING 

The  results  published  here  have  been  obtained  in  the  Co-operative  Work  of 

these  Institutions 


PUBLISHED  MONTHLY  AND  SENT  FREE  TO  CITIZENS  ON  APPLICATION 

Entered  at  the  Postoffice  at  Raleigh,  N.  C.,  as  second-class  matter 
February  7,  1901,  under  Act  of  June  6,  1900. 


Digitized  by  the  Internet  Archive 
in  2019  with  funding  from 
University  of  North  Carolina  at  Chapel  Hill 


https://archive.org/details/plumcurculioonpeOOIeib 


The  Plum  Curculio  on  Peaches  in  North  Carolina 

Its  Life  History  and  Control 

R.  W.  Leiby  and  John  B.  Gill 


During  the  past  few  years  the  control  of  the  plum  curculio  has  be¬ 
come  a  most  important  factor  in  the  growing  of  peaches  in  the  Sand¬ 
hill  section  of  North  Carolina.  This  pest  became  so  serious  in  1921 
that  State  and  Federal  aid  was  requested  to  study  the  insect,  and  to 
instruct  growers  in  the  methods  of  its  control.  Accordingly,  Dr.  R.  W. 
Leiby,  representing  the  Division  of  Entomology  of  the  North  Carolina 
Department  of  Agriculture  and  Experiment  Station,  and  Mr.  John 
B.  Gill,  representing  the  Bureau  of  Entomology  of  the  U.  S.  Depart¬ 
ment  of  Agriculture,  established  a  laboratory  at  Aberdeen,  N.  C.,  dur¬ 
ing  the  season  of  1922.  This  locality  was  in  the  midst  of  a  section  which 
in  1922  produced  1,450  cars  of  peaches. 

The  objects  were  to  ascertain  the  life-history  and  habits  of  the  cur¬ 
culio  by  orchard  and  insectary  studies,  to  conduct  experiments  in  the 
control  of  the  insect  in  the  orchard,  and  to  personally  assist  growers 
in  the  prosecution  of  control  measures  found  previously  to  have  been 
effective  in  Georgia  by  Federal  Avorkers  of  the  Bureau  of  Entomology. 

The  present  bulletin  is  prepared  at  the  request  of  peach  growers  for 
their  future  guidance  in  combating  the  curculio.  It  includes  a  sum¬ 
mary  of  the  life-history  of  the  curculio  as  ascertained  for  the  season 
of  1922  by  the  senior  author  with  the  assistance  of  James  F.  Tarlton,* 
and  the  results  of  field  experiments  conducted  by  the  authors  in  the 
control  of  the  curculio  by  dusting  and  spraying. 

LIFE-HISTORY  AND  HABITS 

The  plum  curculio  is  a  hard  snout  beetle  measuring  about  three  eighths 
of  an  inch  in  length.  This  beetle  is  the  parent  of  the  cream-colored 
legless  grub  or  “worm”  familiar  to  all  peach  growers,  that  is  found  in 
the  small  dropped  fruit,  or  in  ripening  peaches  next  to  the  pit,  where 
its  feeding  has  caused  the  infested  fruit  to  be  Avorthless.  In  North 
Carolina  this  insect  is  knoA\7n  to  also  attack  cultivated  plums,  apples, 
cherries,  and  wild  plums,  the  latter  probably  being  its  native  food  plant. 

This  insect  like  other  beetles  passes  through  four  stages  m  develop¬ 
ing  a  complete  generation;  the  egg  Avhich  is  laid  by  the  parent  beet  e 
under  the  skin  of  the  fruit;  the  larva  which  hatches  from  the  egg  and 
develops  in  the  flesh  of  the  fruit ;  the  pupa  or  resting  stage  which  is 
passed  in  a  small  earthen  cell  in  the  soil;  and  the  adult  or  beetle  stage 
which  develops  from  the  pupal  stage. 

*Temporarily  employed  by  the  Federal  Bureau  of  Entomology  as  laboratory  and  Held 
helper. 


4 


The  Bulletin,  March,  1923 


Hibernation  and  emergence.  The  beetles  hibernate  in  the  woods  ad¬ 
jacent  to  or  near  the  orchard  presumably  under  leaves  or  in  tufts  of 
grass,  and  in  similarly  suitable  places  in  the  orchard.  Most  of  the 
beetles  leave  their  winter  quarters  and  fly  to  the  orchard  early  in  the 
spring  while  others  reach  the  orchard  later.  Thus  in  1922  the  first 
beetle  was  taken  in  the  orchard  on  March  27,  the  number  coming  to 
the  orchard  gradually  rising  till  April  10  when  the  number  decreased 
up  until  May  19.  Hence  the  beetles  came  from  hibernation  to  the 
orchard  over  a  period  of  about  seven  weeks,  the  heaviest  emergence  be¬ 
ing  during  the  week  of  March  30,  when  according  to  the  jarring  records 
approximately  70  percent  of  the  beetles  reached  the  orchard. 

Feeding  and  egg  laying.  Upon  arriving  in  the  orchard  the  beetles 
first  feed  upon  the  unfolding  leaves  and  green  shucks  of  the  blooms;  and 
while  the  shucks  are  being  shed  they  feed  upon  the  young  fruit.  Dur¬ 
ing  this  period  the  beetles  mate. 

In  feeding  upon  the  fruit  two  kinds  of  punctures  are  made,  the  cir¬ 
cular  one  being  usually  a  feeding  puncture  only,  while  the  crescentic 
puncture  usually  indicates  that  an  egg  has  been  laid  in  the  feeding 
puncture  under  the  crescentic  cut.  In  laying  an  egg  in  a  young  peach, 
the  female  first  cuts  through  the  pubescence  of  the  fruit  and  eats  out 
a  small  cavity  under  the  skin.  She  then  turns  about  and  inserts  a 
minute  colorless  egg  into  the  hole.  A  crescentic  shaped  slit  is  then 
cut  in  front  of  and  underneath  the  egg,  which  leaves  the  egg  in  the 
fleshy  flap  of  the  fruit.  However,  eggs  are  frequently  placed  in  simple 
circular  punctures  made  directly  under  the  pubescence  of  the  small 
peach. 

In  1922  the  first  egg  was  found  deposited  in  the  orchard  on  April 
11,  with  a  very  high  percentage  of  the  eggs  laid  within  ten  days  after 
the  shucks  were  shed.  The  insectary  records  show  an  average  of  4.7 
eggs  deposited  each  day  by  individual  females  during  April,  while  in 
May  and  early  June  an  average  of  only  1.5  eggs  was  deposited  daily 
by  individual  females.  The  length  of  the  egg  stage  was  found  to  cover 
a  period  of  three  to  five  days.  A  series  of  128  eggs  in  plums  and  96 
eggs  in  peaches  showed  the  average  length  of  the  egg  stage  during  the 
spring  of  1922  to  be  4.0  and  4.3  days  respectively. 

Development  of  spring  brood  of  larvae*  Upon  emerging  from  the 
egg  the  minute  white  larvae  or  “worms”  bore  into  and  feed  upon  the 
flesh  of  the  young  fruit.  Continued  feeding  causes  the  infested  fruit 
to  become  discolored,  somewhat  shrunken,  and  finally  to  drop,  although 
a  very  few  of  the  small  fruits  may  remain  on  the  trees  until  after  the 
larvae  abandon  the  fruit.  Our  insectary  records  show  that  the  larvae 
become  fully  grown  in  an  average  of  16  days,  whereupon  they  emerge 
from  the  drops  (fig.  1)  and  burrow  into  the  soil.  At  a  depth  of  three 

*The  first  brood  of  beetles  to  develop  in  the  season  from  overwintering  beetles  is 
designated  in  this  circular  as  the  Spring  brood. 

•M 

P 


# 


Plum  Curculio  on  Peaches  5 

or  four  inches  in  loose  sandy  soil,  each  larva  forms  with  the  aid  of 
its  body  a  small  oval  cel]  m  which  it  transforms  to  the  pupal  and  later 

o  the  adult  stage.  Where  the  soil  is  infrequently  or  never  disturbed 
the  earthen  cell  is  made  at  a  depth  of  only  one  or  two  inches. 

During  the  season  of  1922  the  first  larvae  of  the  spring  brood  were 
seen  to  emerge  from  drops  on  April  27,  and  the  last  larvae  emerged  in 
numbers  on  May  26.  Fifty  percent  of  a  total  of  5,212  larvae,  reared 
fiom  dropped  fruit  during  May,  emerged  between  May  3  and  19,  this 
interval  representing  the  peak  of  larval  emergence  for  this  brood  from 
drops.  A  few  larvae  of  this  same  generation  emerge  from  early  varie¬ 
ties  (Mayflower,  Alexander  and  Arp)  as  they  ripen,  which  is  during 
the  latter  part  of  May  and  the  first  half  of  June.  Such  larvae  also 
come  from  eggs  laid  by  overwintering  beetles  in  the  fruits  about  two 
weeks  before  these  early  varieties  ripen.  For  the  most  part,  however, 
the  overwintering  beetles  temporarily  cease  egg  laying  in  the  mid¬ 
season  and  late  varieties  of  fruits,  while  the  latter  are  in  the  stone 
hardening  period.  This  habit  probably  accounts  for  the  fact  as  ex¬ 
perienced  by  growers  that  the  early  varieties  of  peaches  are  seldom 
abnormally  wormy  at  the  time  of  harvest.  It  is  the  development  of 
these  larvae  in  early  varieties  as  they  ripen,  that  prolongs  the  period 
of  larval  emergence  of  this  brood  into  June,  although  as  pointed  out 
above,  the  maximum  emergence  is  between  May  9  and  13  from  the 
small  dropped  fruit. 

Development  of  curculio  and  emergence  from  the  soil — spring  brood. 
The  insect  spends  approximately  a  total  of  31  days  in  the  ground  in 
the  larval,  pupal,  and  adult  stages.  A  series  of  1,037  beetles  reared  in 
cages  in  the  insectary  required  an  average  of  31.2  days  before  the  adults 
emerged,  while  a  series  of  386  beetles  reared  outdoors  in  ground  cages 
in  the  orchard  required  an  average  of  31.5  days  for  emergence.  Of  the 
31  day  period  in  the  ground,  14  days  are  passed  in  the  larval  stage,  12 
days  in  the  pupal  stage,  and  5  days  in  the  beetle  stage.  There  is  no 
evidence  that  the  beetles  remain  in  sandy  soil  until  a  rain  softens  it 
to  facilitate  emergence,  for  they  have  been  observed  to  emerge  readily 
in  very  dry  sandy  soil. 

It  was  ascertained  that  in  1922,  63  percent  of  the  beetles  of  the  spring 
brood  emerged  between  June  9  and  12,  with  the  first  beetle  emerging 
June  1  and  the  last  July  7.  It  is  of  interest  to  note  that  the  number 
of  beetles  caught  by  jarring  increased  perceptibly  about  this  time. 
Thus  the  jarring  records  show  that  6  curculios  were  caught  on  May 
29,  18  on  June  3,  68  on  June  7,  81  on  June  10,  and  72  on  June  14. 
The  beetles  in  the  orchard  at  this  time  (about  June  15)  therefore  be¬ 
long  to  both  the  group  that  overwintered  and  the  recently  developed 
spring  brood,  although  the  number  of  surviving  overwintering  beetles 
in  a  well  cared  for  orchard  is  very  small,  because  of  the  natural 
mortality  and  the  previous  application  of  poison  sprays. 


6 


The  Bulletin,  March,  1923 


Summer  egg  laying  in  late  varieties  of  peaches.1  After  the  beetles  of 
the  spring  brood  emerge  they  feed  upon  fruit  in  the  orchard.  The  in¬ 
sectary  investigations  indicate  that  only  about  20  percent  of  the  females 
of  this  spring  brood  lays  eggs.  It  is  the  combined  egg  laying  of  the 
surviving  overwintering  beetles  and  the  spring  brood  of  beetles,  in  ripen¬ 
ing  mid-season  varieties  and  late  varieties  that  have  passed  through 
the  stone  hardening  period,  that  is  responsible  for  the  development  of 
a  summer  brood2  of  larvae  and  adults,  the  larvae  emerging  in  numbers 
from  the  fruit  at  the  time  that  the  Belle  and  Elberta  varieties  are 
ripening. 

The  egg  laying  records  of  73  beetles  of  the  spring  brood  confined  in 
cages  with  ripening  mid-season  and  green  late  varieties  of  fruit  are 
shown  in  Table  1.  Of  the  73  beetles  (approximately  half  of  which 
were  females)  only  7  deposited  eggs  during  the  49  day  period  of  June 
4  to  July  19  (ripening  period  in  1922  of  Alexander  to  Elberta  varie¬ 
ties).  The  average  number  of  eggs  laid  by  these  seven  females  was 
-46,  or  a  little  less  than  one  egg  per  day  for  each  egg-laying  female 
during  the  49  day  period.  The  records  also  show  that  from  8  to  23 
days  (average  15.6  days)  intervened  between  the  time  of  emergence 
from  the  soil  and  the  laying  of  the  first  egg  by  each  of  the  seven  beetles. 
It  is  of  interest  to  note  that  the  73  beetles  made  a  total  of  4,358  punc¬ 
tures  (feeding  and  egg-laying)  during  the  49  day  period,  an  average 
of  about  60  punctures  for  each  beetle.  Egg-laying  beetles  make  con¬ 
siderably  more  feeding  punctures  than  those  that  do  not  lay  eggs. 

Emergence  of  summer  brood  larvae.  Field  observations  show  that 
the  mid-season  varieties  like  Carman,  Slappey  and  Hiley  are  each 
normally  more  wormy  at  harvest  than  the  preceding  variety.  It  is 
believed  that  this  is  due  to  the  gradual  increase  in  the  number  of 
spring  brood  individuals  laying  eggs  up  until  the  time  that  the  Ililey 
variety  ripens,*  although  during  the  same  period  the  egg  laying  by 
overwintering  beetles  declines. 

The  summer  brood  of  larvae  emerges  from  the  ripening  fruit  over 
a  rather  long  period  of  time,  i.e.  from  approximately  July  4  to  August 
10.  Of  the  larvae  emerging  from  Carman  variety  as  it  ripens,  most 
are  probably  from  eggs  laid  by  overwintering  adults,  and  are  therefore 

1In  the  sandhill  section  of  North  Carolina  the  varieties  ripening  previous  to  Carman 
are  known  as  early  varieties  ;  Carman,  Slappey,  and  Hiley  are  mid-season  varieties  ;  while 
Belle,  Elberta,  and  Hale  are  late  season  varieties.  Since  the  details  of  this  bulletin  are 
intended  to  apply  primarily  to  the  sandhill  section,  the  terms  early,  mid-  and  late 
season  are  here  used  to  include  the  varieties  mentioned  in  their  respective  categories 
above. 

2This  second  brood  is  termed  the  summer  brood  in  this  bulletin  because  it  is  developed 
during  the  period  of  July  and  August. 

*This  opinion  may  appear  to  be  unsound  in  the  case  of  two  adjacent  peach  growers 
where  one  finds  one  variety  (like  Hiley)  more  wormy  than  that  of  his  neighbor  in  the 
same  season.  However,  the  difference  here  would  clearly  be  due  to  ineffective  control 
measures  practiced  by  one  of  the  two  growers.  The  opinion  of  the  writers  is  based  upon 
what  we  believe  would  occur  naturally  in  the  orchard  if  artificial  and  cultural  control 
measures  were  not  instituted. 


Plum  Curculio  on  Peaches 


stiictly  speaking,  first  brood  larvae  although  they  emerge  simultane¬ 
ously  with  some  larvae  that  developed  from  eggs  laid  by  the  spring 
brood  adults.  The  larvae  from  Slappey,  Hiley,  Belle,  Elberta  and 
Hale  are  believed  to  develop  very  largely  from  eggs  laid  by  spring  brood 
adults.  The  brood  of  larvae  emerging  during  July  and  early  August 
is  therefore  predominantly  a  second  brood. 

The  height  of  emergence  of  larvae  of  the  summer  brood  appears  to 
be  about  the  time  that  the  Belle  variety  ripens,  which  in  1922  was  July 
16  to  26;  although  the  Elberta  variety  also  ripened  during  the  latter 
part  of  this  period. 

Einergence  and  habits  of  summer  brood  adults.  The  larvae  of  this 
brood  upon  emerging  from  the  fruit,  burrow  into  the  soil  and  transform 
into  pupae  and  then  into  adult  beetles.  About  31  days  later  the  beetles 
emerge  from  the  soil.  In  1922  most  of  the  beetles  of  this  summer  brood 
emerged  between  August  19  and  26 A 


TABLE  1-INSECTARY  RECORDS  OF  FEEDING  AND  EGG  LAYING  ACTIVITIES  OF  SPRING 
BROOD  BEETLES  BETWEEN  JUNE  4  AND  JULY  19,  1922* 


EXPERI¬ 

MENT 

NO. 

CURCULIOS 

iif 

EXPERIMENT 

CURCULIOS 

LAYING 

EGGS 

TOTAL 

NUMBER  OF 

EGGS  LAID 

BY 

CURCULIOS 

DATE 

FIRST  EGG 

LAID 

DAYS  AFTER 

EMERGENCE 

FIRST  EGG 

WAS  LAID 

NUMBER  OF 

PUNCTURES 

MADE 

1 

2 

o 

0 

127 

2 

6 

1 

49 

June 

22 

19 

468 

3 

10 

1 

36 

June 

18 

14 

591 

4 

10 

1 

55 

June 

27 

23 

618 

5 

8 

o 

0 

252 

6 

8 

1 

53 

June 

14 

8 

679 

7 

6 

o 

0 

307 

8 

9 

1 

12 

June 

21 

14 

578 

9 

14 

2 

116 

June 

22 

15 

738 

June 

23 

16 

Total 

73 

7 

321 

4358 

Average 

46 

June 

21 

15.6 

60 

*Discontinued  insectary  studies  on  this  date  in  order  to  examine  the  harvested  fruit  of  the  expeii 
mentally  sprayed  and  dusted  plats  in  the  orchard. 


At  the  time  of  maximum  emergence  of  the  summer  brood  of  beetles, 
all  commercial  varieties  of  peaches  have  been  harvested.  The  beetles 
then  feed  upon  the  foliage  or  upon  scattered  fruit  left  on  the  tiees.  If 
peaches  were  available  after  emergence  ol  the  beetles,  it  is  possible 
that  a  third  brood  of  beetles  could  be  reared  in  the  same  season.  So 
far  as  known,  however,  a  third  brood  is  not  developed  in  peaches  in 

North  Carolina. 

About  September  first  the  beetles  in  the  orchard,  according  to  our 
life-history  studies,  would  represent  both  spring  brood  and  summer 


♦Data  based  on  limited  observations. 


8 


The  Bulletin,  March,  1923 


brood  beetles.  It  is  even  possible  that  a  stray  overwintering  beetle 
may  be  found  at  this  time.  The  senior  writer  has  kept  overwintering 
beetles  collected  March  29  alive  in  cages  until  August  16  by  supplying 
them  with  abundant  fresh  foliage  and  fruit.  At  the  approach  of  cold 
weather,  the  beetles  migrate  from  the  orchard  to  the  woods  Jr  to  suitable 
hibernating  places,  there  to  pass  the  winter  and  emerge  the  following 
spring. 

INSECT  ENEMIES 

Two  kinds  of  insect  parasites,  one  a  small  four  winged  fly,  Triaspis 
curculionis  Bitch,  and  another,  a  true  two  winged  fly,  Myophasia  glo- 
bosa  Twnsd,  were  reared  from  the  larvae  during  the  summer  of  1922. 
The  former  species  was  reared  in  early  June  and  the  latter  species  in 
late  July  and  early  August.  Neither  of  these  parasites  was  bred  in 
any  numbers  that  would  appreciably  reduce  the  curculio  infestation. 

Ants  are  believed  to  be  somevdiat  efficient  in  reducing  the  numbers 
of  curculio  larvae.  They  were  frequently  observed  in  the  act  of  de¬ 
vouring  curculio  larvae  when  placed  on  the  soil  among  or  near  the  ants. 

EXPERIMENTS  IN  CONTROL 

The  control  experiments  carried  out  during  the  season  1922  con¬ 
sisted  of  dusting  or  spraying  three  blocks  of  Elberta  trees  to  compare 
the  effectiveness  of  these  methods  of  application  of  materials ;  the  spray¬ 
ing  of  two  blocks  of  the  Belle  variety  from  one  of  which  the  drops  were 
picked  up  to  determine  the  value  of  picking  up  the  drops;  and  the 
burning  over  of  a  portion  of  the  waste  land  on  one  side  of  an  orchard, 
to  ascertain  the  effectiveness  of  this  practice  for  the  destruction  of 
hibernating  curculios.  The  insectary  control  experiments  included  a 
study  of  the  resistance  of  beetles  to  various  strengths  of  poison,  and  a 
study  of  the  effect  of  rains  upon  foliage  and  fruit  recently  treated  with 
poison. 

The  field  dusting  and  spraying  experiments  were  conducted  in  the 
orchards  of  the  Hoffman  Barms,*  Hoffman,  N.  C.  The  jarring  records 
secured  in  connection  with  the  burning  of  an  area  adjacent  to  an  orch¬ 
ard  were  ascertained  in  one  of  the  Halbert  Blue*  orchards  at  Aberdeen. 

The  experiments  were  primarily  designed  to  secure  comprehensive 
evidence  of  the  value  of  the  control  recommendations  given  to  com¬ 
mercial  peach  growers  throughout  the  season  in  circulars  and  by  per¬ 
sonal  visitation,  and  to  ascertain  the  adaptability  of  the  recommenda¬ 
tions  to  the  sandhill  section  of  North  Carolina.  The  control  recom¬ 
mendations  advocated  to  growers  originated  in  part  from  the  work  of 
the  Bederal  Bureau  of  Entomology  in  Georgia,  and  were  a  modification 
of  those  previously  advocated  by  the  Division  of  Entomology  of  this 
State. 

*The  thanks  of  the  writers  are  due  Messrs.  W.  R.  Land,  Reid  Page  and  U.  R.  Simp¬ 
kins,  owners  of  Hoffman  Farms,  and  to  Halbert  Blue,  for  their  kindness  in  placing  these 
orchards  at  our  disposal  for  experimental  purposes. 


9 


Plum  Curculio  on  Peac 


hes 


Field  Dusting  and  Spraying  Experiments— Elberta  Variety 

i/orr:r/.vrr;rb£St‘r  r*- '» t™" 

k«  well  «t  witt  fruit.  This  oreh.ri  had  ,  „re»*i„Tfit«L  !fm“ 
o  approximately  60  percent,  m  spite  of  the  fact  that  it  had  been  fre¬ 
quently,  but  irregularly  sprayed.  All  waste  lands  about  the  orchard 
had  been  burned  over  in  the  early  spring  of  1922. 

Description  and  treatment  of  plats.  Plat  I  consisted  of  35  trees  re- 
ceived  no  treatment  and  was  used  as  a  check  against  the  other  plats. 
Plat  II  consisted  of  S4  trees  and  was  sprayed  three  times.  Plat  III  con¬ 
sisted  of  90  trees  and  was  sprayed  four  times.*  Plat  IV  consisted  of 
1 8  trees  and  was  dusted  four  times.*  The  dates  of  application,  material 
and  formulas  used,  are  shown  m  table  2.  It  should  be  noted  that  all 


Fig.  1.  Curculio  larvae  are  commonly  developed  in  drops.  These  should 
be  picked  up  before  the  larvae  emerge  and  none  should  he  overlooked.  (From 
U.  S.  D.  A.  Circular  216  by  Snapp,  Turner  and  Roberts). 


drops  were  regularly  picked  up  from  all  trees  except  those  in  the 
check-plat  1. 

The  first  application  was  made  on  plats  III  and  IV  immediately 
after  the  petals  had  fallen,  this  application  being  omitted  on  plat  II. 
The  second  application  was  made  on  all  treated  plats  just  after  the 


*The  regular  schedule  growers  were  advised  to  use. 


10 


The  Bulletin,  March,  1923 


WASTE  LAND 


PLAT  I 
CHECK 
35  TREES 

PLAT  H 

3  SPRAYS 
84-  TREES 

PLAT  m 

4  SPRAYS 
90  TREES 


PLAT  ET 
4  DUSTS 
18  TREES 


Q 

— 3 
Uj 

U 

O 

CJ 

h~ 

< 

> 


Z3 

o 


PLAT  sn 
4  SPRAYS 
PICK  UP  DROPS 
89  TREES 


PLATE 
4  SPRAYS 
LEAVE  DROPS 
81  TREES 


PLAT  ¥ 
CHECK 
Z0  TREES 


31  ROWS  ELBERTA 
AND  GEORGIA  BELLE 


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HIGHWAY 
LIGHT  WOODS 


Fig.  2.  Diagram  of  orchard  experimental  plats.  The  circles  represent  the 
location  of  trees ;  the  solid  circles  the  count  or  record  trees  selected  in  each 
plat ;  while  the  crosses  represent  missing  or  replanted  trees.  Hoffman  Farms, 
Hoffman,  N.  C.,  1922. 


Plum  Curculio  on  Peaches 


11 


shucks  were  shed.  The  third  application,  made  on  all  treated  plats 
was  given  two  weeks  after  the  second ;  and  the  fourth  was  made  on  all 
treated  plats  about .  a  month  before  the  variety  ripened.  The  dates 
upon  which  all  applications  were  made  are  given  in  table  2. 

In  all  spraying  either  a  Bean  Triplex  200-gallon  sprayer  or  a  Friend 
100-gallon  sprayer  was  used  at  a  pressure  of  175  to  200  pounds.  The 
sprayers  were  fitted  up  with  two  leads  of  hose  and  two  nozzles  to  each 
lead.  The  dusting  machine  used  was  a  Niagara  model  Dl-2.  A  total 
of  427  gallons  of  spray  was  used  in  three  applications  to  plat  II  (84 
trees)  ;  533  gallons  in  four  applications  to  plat  III  (90  trees)  ;  and  a 
total  of  152  pounds  of  dusting  mixture  was  used  in  four  applications 

on  plat  IV  (78  trees).  All  of  the  liquid  and  dry  applications  were 
made  thoroughly. 

After  the  fruit  had  set,  ten  trees  known  as  record  or  count  trees 
(designated  by  solid  circles  in  the  plats  in  figure  2)  were  selected  in 
or  near  the  center  of  each  plat,  and  these  were  marked  by  muslin  bands. 
From  each  of  the  ten  record  trees  in  each  of  the  four  plats,  a  record 
of  each  drop  and  harvested  fruit  was  secured.  It  is  from  these  record 
trees  that  the  percentage  of  infestation  by  curculio  in  the  drops  and 
harvested  fruit  was  ascertained,  the  assumption  being  that  each  ten 
trees  represented  the  curculio  infestation  in  its  respective  plat. 

A  total  of  16  examinations  of  different  pickings  of  drops  from  the 
record  trees  was  made  on  plat  I,  and  14  examinations  on  each  of  plats 
II,  III  and  IV.  These  examinations  were  made  between  April  25  and 
July  24  with  most  of  the  examinations  made  during  the  latter  part  of 
April  and  in  May.  A  total  of  5,319  drops  was  examined  from  the  ten 
record  trees  of  plat  I,  3,198  from  plat  II,  4,211  from  plat  III  and  2,829 
from  plat  IV,  making  a  grand  total  of  15,557  drops  examined  on  the 
four  plats. 

The  fruit  was  harvested  in  four  different  pickings  made  between 
July  24  and  28.  The  ten  record  trees  of  plat  I  yielded  4,645  fruits  at 
harvest,  those  of  plat  II  yielded  4,646  fruits,  those  of  plat  III  yielded 
6,359  fruits  and  those  of  plat  IV  yielded  4,414  fruits  or  a  total  of  20,064 
fruits  harvested  on  the  four  plats. 

A  grand  total  of  35,621  drops  and  harvested  fruit  was  examined  from 
the  40  record  trees  of  the  four  plats. 

Discussion  of  results ,  The  percentage  of  curculio  wormy  drops  and 
harvested  fruit  of  the  ten  record  trees  in  each  of  the  four  plats  is  shown 
in  table  2.  The  drops  in  the  check  were  63.62  percent  wormy;  those 
of  plat  II  sprayed  three  times  were  16.57  percent  wormy;  those  of 
plat  III  sprayed  four  times  were  8.34  percent  wormy  indicating  that 
the  drops  in  the  check  were  nearly  eight  times  as  wormy  as  those  ol  the 
plat  sprayed  four  times.  The  dropped  fruit  of  plat  IV  dusted  four 
times  showed  8.55  percent  worminess  or  about  the  same  as  that  ot  plat 
III  sprayed  four  times. 


12 


The  Bulletin,  March,  1923 


TABLE  2—  CURCULIO  INFESTATION  OF  FRUIT  OF  TEN  TREES  IN  EACH  OF  FOUR  ELBERTA 
PLATS— DROPS  AND  HARVESTED  FRUIT.  PLATS  II  AND  III  WERE  SPRAYED;  PLAT  IV 
DUSTED.  ALL  DROPS  PICKED  UP  REGULARLY  FROM  PLATS  II.  Ill  AND  IV. 
HOFFMAN,  N.  C.,  1922 


* 

Percentage  of  fruit  wormy 

Plat 

No. 

Dates 

TREATED 

Material 

USED 

Formula 

Drops 

Harvested 

fruit 

Drops  and 

HARVESTED 

FRUIT 

I 

Check 

No 

Treatment 

None 

None 

63.62 

37.71 

52.46 

II 

3  Sprays 

Apr.  12 
Apr.  26 
June  21 

AL-L 

SBLS-AL 

SBLS-AL 

1-3-50 

8-8-1-50 

8-8-1-50 

16.57 

8.91 

12.03 

III 

4  Sprays 

Apr.  4 
Apr.  12 
Apr.  26 
June  21 

AL-L 

AL-L 

SBLS-AL 

SBLS-AL 

1-3-50 

1-3-50 

8-8-1-50 

8-8-1-50 

8.34 

6.13 

7.01 

IV 

4  Dusts 

Apr.  4 
Apr.  13 
May  1 
June  22 

S-AL-L 

S-AL-L 

S-AL-L 

S-AL-L 

80-5-15 

80-5-15 

80-5-15 

80-5-15 

• 

8.55 

5.69 

6.81 

Key  to  table.  AL-L — Arsenate  of  lead  and  lime;  SBLS-AL — Self-boiled  lime-sulphur  and  arsen¬ 
ate  of  lead;  S-AL-L — Sulphur,  arsenate  of  lead  and  lime.  1-3-50 — one  pound  powdered  lead  arsenate, 
3  pounds  stone  lime  and  50  gallons  of  water;  8-8-1-50 — 8  pounds  sulphur,  8  pounds  stone  lime,  1  pound 
lead  arsenate  and  50  gallons  of  water;  80—5—15 — dusting  formula  of  80  pounds  sulphur,  5  pounds  arsen¬ 
ate  of  lead,  and  15  pounds  hydrated  lime. 

It  should  be  stated  that  the  drops  included  not  only  the  small  fruits 
that  fell  when  they  were  small  (fig.  1),  but  those  which  were  nearly 
full  grown  or  entirely  grown,  and  fell  normally,  up  until  the  time  of 
picking.  There  were  relatively  more  of  the  drops  of  the  latter  class  in 
the  check  plat  than  in  any  of  the  other  plats,  and  some  of  these  full 
grown  drops  nearly  all  of  which  were  wormy,  might  have  well  been  in¬ 
cluded  as  harvested  fruit.  This  would  decrease  the  percentage  of  wormi¬ 
ness  of  drops  but  increase  percentage  of  worminess  of  harvested  fruit. 

As  table  2  indicates  37.71  percent  of  the  harvested  fruit  of  the  check 
was  wormy.  This  percentage  was  reduced  in  the  adjacent  plat  II  to 
8.91  percent,  the  plat  having  been  sprayed  three  times  and  having  the 
first  application,  made  on  plats  III  and  IV,  omitted.  The  control  on 
plat  II  is  unusually  good  in  view  of  its  location,  one  end  of  it  having 
been  adjacent  to  unwooded  waste  land. 

Plats  III  and  IV  which  were  sprayed  and  dusted  four  times  each 
respectively  showed  their  harvested  fruit  to  be  6.13  aud  5.69  percent 
wormy.  The  difference  of  .44  percent  worminess  in  favor  of  plat  IV 
might  safely  be  charged  to  the  location  of  this  plat,  which  was  seven 
rows  farther  from  the  unwooded  waste  land  than  the  location  of  plat 
III. 

The  writers  feel  that  the  percentages  of  worminess  are  representative 
of  the  various  plats.  It  is  true  that  the  check  (plat  I)  was  located  at 
one  end  of  the  orchard,  and  it  was  on  this  account  subject  to  greater 


Plum  Curculio  on  Peaches 


13 


curculio  attack  by  reason  of  its  location  next  to  unwooded  waste  land ;  but 
on  tlie  other  hand  the  trees  in  this  plat  were  more  vigorous,  larger,  and 
bore  more  fruit  (drops  and  harvested  fruit)  by  27  percent  than  those 
of  plat  II,  and  37  percent  more  than  plat  IY,  although  6  percent  less 
than  those  of  plat  III.  If  the  diseases — scab  and  brown  rot — were  in¬ 
cluded  in  the  check,  the  percentage  of  unmarketable  fruit  would  be,  of 
course,  somewhat  greater. 

Experiment  to  Ascertain  Value  of  Picking  up  Dropped  Fruit — Belle  Variety 

This  experiment  was  conducted  in  the  opposite  end  of  the  orchard 
from  that  in  which  the  spraying  and  dusting  experiments  were  con¬ 
ducted.  The  variety  selected  was  Belle.  The  trees  were  six  years  old. 

Description  and  treatment  of  plats.  Three  plats  of  trees  were  used 
in  this  experiment  (see  diagram  on  page  10).  Plat  Y  consisting  of  20 
trees  served  as  a  check  and  received  no  treatment.  Plats  YI  and  YII 
consisting  of  81  and  89  trees  respectively  were  sprayed  exactly  as  de¬ 
scribed  for  plat  III  (except  for  the  dates  of  application  which  are 
given  in  table  3)  ;  but  the  drops  were  picked  up  regularly  between  April 
25  and  May  21  on  plat  YII  and  left  on  the  ground  in  plat  YI.  Else¬ 
where  in  the  general  orchard,  which  was  sprayed  four  times,  the  drops 
were  picked  up. 

As  in  plats  I  to  IY,  ten  record  trees  were  selected  in  approximately  the 
center  of  each  plat  early  in  the  season.  Each  drop  and  harvested  fruit 
from  these  record  trees  was  examined  for  curculio,  brown  rot,  and  scab. 
The  record  of  each  ten  trees  was  taken  as  representative  of  the  infesta¬ 
tion  in  its  respective  plat.  A  total  of  4,343  drops  and  14,6/5  harvested 
fruits  was  examined  from  the  30  record  trees  of  the  three  plats. 

Discussion  of  results.  As  is  shown  in  table  3,  the  check  (plat  Y)  was 
found  to  have  31.5  percent  of  its  harvested  fruit  wormy.  In  plat  YII 
where  the  drops  were  picked  up,  only  0.61  percent  of  the  harvested  fruit 
was  wormy.  In  plat  YI  where  the  drops  were  left  on  the  giound,  ^.0o 
percent  of  the  harvested  fruit  was  found  wormy.  These  results  indi¬ 
cate  that  the  plat  where  the  trees  were  sprayed  and  the  drops  picked 
up  was  only  one  fiftieth  as  wormy  at  harvest  as  the  check  plat ;  and 
that  the  plat  where  the  trees  were  sprayed  but  the  drops  left  on  the 
ground  was  one  fifteenth  as  wormy  as  the  check  plat.  The  figures  further 
indicate  that  the  plat  where  the  drops  were  left  on  the  ground,  was  more 
than  three  times  as  wormy  as  the  plat  where  the  drops  were  picked  up. 

If  the  spring  bred  brood  of  beetles  is  an  important  factor  in  causing 
the  fruit  as  it  ripens  to  become  wormy  to  an  appreciable  extent,  we 
should  expect  the  plat  in  which  the  drops  were  not  picked  up  to  be  more 
wormv  at  harvest  than  it  proved  to  be.  We  should  expect  it  to  have 
shown  perhaps  as  much  as  ten  to  twenty  percent  worminess.  Ihe  toi- 
lowing  statement  of  conditions  as  observed  during  the  season  on  these 


14 


The  Bulletin,  March,  1923 


plats  may  explain  why  the  harvested  fruit  in  the  plat  where  the  drops 
were  left  on  the  ground  did  not  show  greater  worminess. 

A  study  of  the  activity  of  the  curculio  during  the  season,  indicated 
that  the  migration  of  adult  beetles  into  this  end  of  the  orchard  was  late. 
The  early  drops  were  comparatively  free  of  worms  while  the  later  drops 
were  suprisingly  heavily  infested.  It  appeared  that  the  later  infestation 
was  due  largely  to  egg  laying  by  spring  brood  curculios  which  were 
reared  in  a  wild  plum  thicket  nearby.  Because  of  this  late  migration 
into  the  orchard,  the  drops  and  harvested  fruit  of  the  check  plat  were 
quite  wormy,  while  those  of  the  sprayed  plats  VI  and  VII  were  com- 


TABLE  3— CURCULIO  I  NFESTATION  0 F  FRUIT  0  F  TEN  TR EES  I  N  EACH  OF  THREE  PLATS, 
BELLE  VARIETY— DROPS  AND  HARVESTED  FRUIT.  PLATS  VI  AND  VII  SPRAYED  ALIKE. 
DROPS  PICKED  UP  ON  PLAT  VII  BETWEEN  APRIL  25  AND  MAY  1,  AND  LEFT  ON  THE 
GROUND  IN  PLAT  VI.  HOFFMAN,  N.  C.,  1922. 


Percentage  of  fruit  wormy 

Plat 

No. 

Dates 

TREATED 

Material 

USED 

Formula 

Drops 

Harvested 

fruit 

Drops  and 

HARVESTED 

FRUIT 

V 

No 

Treatment 

None 

None 

41.67 

• 

31.50 

34.27 

VI 

Apr.  4 
Apr.  14 
May  1 
June  14 

AL-L 

AL-L 

SBLS-AL 

SBLS-AL 

1-3-50 

1-3-50 

8-8-1-50 

8-8-1-50 

2.71 

2.03 

2.17 

VII 

Apr.  4 
Apr.  14 
May  1 
June  14 

AL-L 

AL-L 

SBLS-AL 

SBLS-AL 

1-3-50 

1-3-50 

8-8-1-50 

8-8-1-50 

1.19 

0.61 

0.73 

Note. — For  key  to  mixtures  and  formulas  see  bottom  of  table  2. 


paratively  free  of  worms.  If  both  sprayed  plats  had  been  infested 
early  in  the  season  so  that  an  appreciable  spring  brood  could  have  been 
reared  in  the  drops  of  these  plats,  the  difference  in  the  percentage  of 
worminess  of  the  two  plats  at  harvest  would  doubtless  have  been  con¬ 
siderably  greater.  The  results  of  this  experiment  appear  therefore 
somewhat  inconclusive.  However,  if  the  increased  percentage  of  worm 
free  fruit,  secured  in  the  block  where  the  drops  were  picked  up,  is  ex¬ 
pressed  in  terms  of  commercial  crates  the  value  of  the  increase  will  be 
found  greater  than  the  cost  of  this  control  operation. 

Worminess  of  drops  during  the  season.  In  connection  with  the  value 
of  picking  up  the  drops,  it  may  be  stated  here,  that  the  drops  which 
had  been  picked  up  in  various  orchards  were  brought  to  the  insectary 
throughout  the  growing  season,  and  the  percentage  of  worminess  as¬ 
certained  by  rearing  the  larvae  from  them.  The  percentage  of  wormi¬ 
ness  was  found  to  vary  greatly.  The  higher  percentages  of  worminess 
were  nearly  always  secured  from  drops  picked  up  beneath  trees  that 


Plum  Curculio  on  Peaches 


15 


were  growing  near  wooded  or  waste  land.  In  one  instance  a  bushel  of 
drops  composed  of  5,338  fruits  yielded  3,012  larvae— an  infestation  of 
56.43  percent.  These  drops  which  were  comparatively  small  were  picked 
up  on  May  5,  at  the  time  when  the  third  picking  was  advocated  to 
growers. 


Fig.  3.  Dusting  in  a  peach  orchard.  It  is  best  to  proceed  down  each  tree 
row  and  dust  only  on  one  row  at  a  time.  (From  U.  S.  D.  A.  Circular  216  by 
Snapp,  Turner  and  Roberts). 

Experiment  in  Burning  over  Waste  Lands  to  Destroy  Hibernating  Beetles 

On  March  9,  one  half  of  the  lightly  wooded  land  adjacent  to  one 
side  of  an  orchard  of  twelve-year-old  Elberta  trees  was  burned  over, 
while  the  other  half  was  not  burned.  A  better  than  average  burn  was 
secured.  A  series  of  44  trees  known  as  block  A  was  then  selected  in 
that  part  of  the  orchard  opposite  the  burned-over  area,  and  a  similar 
series  of  42  trees  known  as  block  B  was  selected  opposite  the  unburned 
area.  A  third  series  of  39  trees  was  selected  on  another  side  of  the 
orchard  adjacent  to  a  cultivated  field.  The  trees  selected  in  each  block 
extended  six  and  seven  rows  deep  into  the  orchard.  The  tiees  veic 
then  jarred  for  curculios  over  a  canvas  frame,  an  average  of  about 
twice  a  week  from  March  14  to  August  9.  The  records  of  the  beetles 
taken  are  of  interest  in  connection  with  this  experiment  up  until  May 
19  when  new  spring  reared  beetles  were  found  in  the  orchard. 


16 


The  Bulletin,  March,  1923 


Results  and  discussion  of  experiment.  According  to  the  totals  shown 
in  table  4,  730  beetles  were  jarred  from  the  block  of  44  trees  located 
opposite  that  part  of  the  woods  which  was  not  burned  over,  while  265 
beetles  were  secured  from  a  similar  block  of  42  trees  located  opposite 
that  part  of  the  woods  which  was  burned  over.  The  block  of  39  trees 
located  adjacent  to  a  cultivated  field,  yielded  a  total  of  111  beetles.  The 
figures  indicate  that  the  burning  over  of  the  wooded  land  was  of  value 


Fig.  4.  Spraying  in  a  peach  orchard,  using  two  leads  of  hose  and  applying 
the  spray  to  two  rows  at  a  time.  (From  U.  S.  D.  A.  Circular  216  by  Snapp, 
Turner  and  Roberts.) 


in  that  the  burning  reduced  the  number  of  beetles  by  62  percent.  They 
also  indicate  that  only  17  percent  of  the  number  that  entered  the  orch¬ 
ard  from  block  opposite  the  unburned  area,  entered  the  cultivated  field 
side. 


Laboratory  Poisoning  Experiments 

Following  each  application  of  the  recommended  schedule,  attention 
was  given  to  ascertaining  the  effect  of  various  strengths  of  poison  upon 
the  beetles.  Many  twigs  were  pulled  from  trees,  that  had  either  been 
sprayed  or  dusted  under  orchard  conditions,  and  brought  to  the  in¬ 
sectary.  From  15  to  30  healthy  curculios  were  then  introduced  in  each 
cage  containing  one  or  two  twigs,  and  the  length  of  time  ascertained 
until  all  the  curculios  died  as  a  result  of  feeding  upon  the  poisoned 


Plum  Curculio  on  Peaches 


17 


TABLE  4  COMPARISON  OF  NUMBER  OF  BEETLES  JARRED  FROM  THREE  BLOCKS  OF  12- 
YEAR-OLD  ELBERTA  PEACH  TREES  BETWEEN  MARCH  14  AND  MAY  19,1922  WOODED 
LAND  OPPOSITE  HALF  OF  ONE  SIDE  OF  ORCHARD  WAS  BURNED  OVER  MARCH  9 
ABERDEEN.  N.  C. 


Date  jarred 

Number 

OF  BEETLES  SECURED  FROM 

44  TREES  OPPOSITE 
UNBURNED  WOODS 

42  TREES  OPPOSITE 
BURNED-OVER 
WOODS 

39  TREES  NEXT 

TO  FIELD 

March 

14,  16,  21,  24 

0 

0 

o 

i  4 

27 

7 

0 

0 

29 

64 

14 

1 

31 

247 

110 

17 

April 

3 

66 

31 

6 

5 

124 

46 

36 

8 

37 

20 

5 

10 

92 

16 

18 

13 

37 

6 

10 

4  4 

15 

9 

6 

2 

4  4 

18 

14 

1 

4 

4  4 

21 

9 

2 

2 

4  « 

24 

2 

0 

0 

May 

5 

7 

5 

1 

4  4 

9 

8 

2 

4 

4  4 

13 

4 

5 

4 

4  i 

19 

3 

1 

1 

Total  beetles 

730 

265 

111 

Total  beetles  on  basis  of 

44  trees  to  each  block 

730 

278 

125 

foliage.  Similar  curculios  were,  of  course,  placed  in  similar  cages  con¬ 
taining  unpoisoned  foliage.  In  general  it  was  found  that  the  beetles 
lived  five  to  eight  days  before  death  ensued,  after  they  had  fed  upon 
foliage  and  fruit  which  had  been  sprayed  at  the  rate  of  one  pound  of 
powdered  lead  arsenate  to  50  gallons  of  water.  It  was  noted,  however, 
that  the  beetles  were  usually  quite  inactive  after  the  third  day  of  ex¬ 
posure  to  sprayed  fruit,  and  that  after  this  time  they  fed  very  little 
and  deposited  no  eggs.  It  is  quite  obvious  that  the  beetles  are  strongly 
resistant  to  arsenical  poisons. 

In  connection  with  the  poisoning  experiments  we  have  observed  that 
moderately  heavy  showers  following  a  spray  or  dust  application  w ithin 
twelve  to  twenty-four  hours,  decrease  very  decidedly  the  effectiveness 
of  the  poison  in  the  spray  or  dust.  The  insectary  studies  on  this  phase 
indicate  very  conclusively  that  the  greater  the  amount  of  rainfall  fol¬ 
lowing  an  orchard  spray  or  dust  treatment,  the  longer  the  interval  be¬ 
tween  the  feeding  of  the  curculio  on  this  foliage  and  its  resultant  death 

by  arsenical  poisoning. 

CURCULIO  CONTROL  RECOMMENDATIONS 

Experience  has  shown  that  in  order  to  grow  peaches  commercially 
and  reasonably  free  of  curculio  injury,  it  is  necessary  to  practice  sever  a 
control  measures  systematically  which  extend  throughout  the  growing 
season.  These  control  operations  may  be  listed  under  four  heads :  (  ) 


18 


The  Bulletin,  March,  1923 


orchard  sanitation,  (2)  applications  of  spray  or  dust  mixtures,  (3) 
picking  up  of  dropped  fruit,  and  (4)  cultivation. 

It  is  a  matter  of  common  observation  that  during  the  season  1922, 
the  cleanest  fruit  in  the  sandhill  section  was  grown  in  the  orchards 
where  owners  carried  out  each  of  these  measures  assiduously;  and  that 
such  growers  who  neglected  one  or  more  of  these  operations,  or  were 
careless  in  executing  the  recommendations,  suffered  curculio  injury 
proportionately.  We  know  of  growers  who  were  disappointed  with  their 
results  when  their  harvested  fruit  showed  a  small  amount  of  worminess. 
Careful  inquiry  in  some  cases  indicated  that  such  growers  failed  to  re¬ 
duce  the  worminess  to  the  degree  hoped  for  because  of  various  reasons. 
Among  these  were,  the  failure  to  make  a  spray  or  dust  application  at 
the  proper  time,  the  alteration  of  formulas  of  spray  mixtures  which 
were  recommended,  and  the  carelessness  in  picking  up  all  drops.  Suc¬ 
cessful  control  of  the  curculio  (and  so  far  as  our  experience  shows  the 
brown-rot  and  scab  as  well)  can  only  he  obtained  by  adhering  rigidly 
to  the  schedule  and  details  of  the  following  recommendations. 

Orchard  Sanitation 

Since  the  curculio  is  known  to  spend  the  winter  in  sheltered  places 
in  woodlands,  waste  lands,  or  in  piles  of  rubbish  in  or  adjacent  to  peach 
orchards,  it  is  obvious  that  it  will  he  of  advantage  to  reduce  the  num¬ 
bers  of  beetles  by  cleaning  up  such  places.  When  the  edge  of  the  or¬ 
chards  do  not  furnish  suitable  hibernating  places,  the  beetles  will  of 
necessity  search  further  away  from  the  orchard  for  suitable  quarters. 
This  increases  the  hazards  for  their  successful  return  the  following 
spring. 

Our  experiment  in  burning  over  wooded  land  adjacent  to  the  orchard 
indicates  the  advisability  of  this  practice  at  least  as  far  as  a  control 
measure  for  the  curculio  is  concerned.  It  seems  advisable  that  the 
burning  should  extend  200  to  300  yards  from  the  orchard.  The  burn¬ 
ing  must  he  done  thoroughly  however;  and  this  means  that  the  vegeta¬ 
tion  and  rubbish  must  he  entirely  dry  at  the  time  of  burning;  otherwise 
the  fire  will  not  burn  close  to  the  ground,  and  some  beetles  will  in  con¬ 
sequence  escape  the  burn.  Precautions  in  burning  are,  of  course,  neces¬ 
sary  and  essential.  Burning  should  never  be  done  without  competent 
supervision  and  sufficient  labor  to  cope  with  any  emergency  that  may 
arise.  . 

Spraying  and  Dusting  Applications 

The  spraying  schedule  previously  recommended  by  the  bforth  Caro¬ 
lina  Department  of  Agriculture  and  Experiment  Station  but  modified 
by  workers  of  the  Federal  Bureau  of  Entomology  at  Fort  Valley,  Ga., 
and  recommended  to  peach  growers  in  this  State  during  1922,  has  been 
found  satisfactory  for  the  curculio  both  by  the  growers  and  in  our  own 
orchard  tests.  The  brown-rot  and  scab  diseases  are  seldom  a  serious 


Plum  Curculio  on  Peaches 


19 


Fig.  5.  View  of  ground  rearing  cages  and  insectary.  Aberdeen,  N.  C.,  1922. 


Fig.  6.  .  Trays  for  rearing  curculio  larvae  from  drops,  and  insectary.  Aber¬ 
deen,  N.  C.,  1922. 


20 


The  Bulletin,  March,  1923 


factor  in  the  sandhill  section,  but  the  schedule  has  also  proved  satisfac¬ 
tory  for  the  control  of  these  diseases  in  the  peach  sections  of  Georgia. 
It  is  reasonable  to  expect  that  this  schedule  will  control  brown-rot  and 
scab  in  the  sandhill  section  of  this  State;  though  it  may  be  found  ad¬ 
visable  at  times  to  make  an  extra  application  of  self-boiled  lime-sulphur 
as  a  spray,  or  dry  sulphur  as  a  dust,  a  week  or  ten  days  before  the  late 
varieties  ripen.  According  to  our  present  knowledge  all  varieties  ripen¬ 
ing  later  than  Carman  should  receive  all  four  applications  of  either 
schedule,  although  in  some  seasons  it  may  be  advisable  to  also  make 
four  applications  on  Carman.  Varieties  ripening  previous  to  the  Car¬ 
man  should  receive  three  applications  of  dust  or  spray  which  are  to  be 
made  at  the  times  recommended  in  the  schedules  for  the  first,  second, 
and  fourth  treatments. 


Spraying  Schedule 

First  application.  Immediately  after  the  petals  fall,  use  one  pound 
of  powdered  arsenate  of  lead,  plus  lime  water  in  which  3  pounds  of 
good  stone  lime  has  been  slaked,  to  each  50  gallons  of  water. 

Second  application.  When  the  calyces  or  shucks  are  shedding,  which 
is  about  ten  days  after  the  falling  of  the  petals,  use  the  same  spray  as 
for  the  first  application. 

Third  application.  Two  weeks  after  the  second  application  or  about 
four  weeks  after  the  petals  have  fallen,  use  1  pound  of  powdered  arsen¬ 
ate  of  lead  with  each  50  gallons  of  8-8-50  self-boiled  lime-sulphur. 

Fourth  application.  About  four  weeks  before  each  variety  is  due 
to  ripen,  use  the  same  spray  as  recommended  for  the  third  application. 

Dusting  Schedule 

The  80-5-15  mixture  composed  of  80  percent  sulphur,  5  percent  arsen¬ 
ate  of  lead,  and  15  percent  hydrated  lime  is  recommended  for  dusting. 
The  applications  should  be  made  at  the  same  times  that  the  spray  appli¬ 
cations  are  recommended,  the  same  dusting  formula  being  used  for  all 
dust  applications.  The  times  for  dusting  applications  are,  first,  im¬ 
mediately  after  the  petals  have  fallen;  second,  when  the  calyces  or 
shucks  are  shedding ;  third,  two  weeks  after  the  second  application ; 
fourth,  about  four  weeks  before  each  variety  is  due  to  ripen. 

Directions  for  Preparing  Spray  Mixtures 

Lead-lime-water  mixture.  Slake  three  pounds  of  stone  lime  in  a  small 
quantity  of  water  and  dilute  to  50  gallons.  Mix  one  pound  of  powdered 
arsenate  of  lead  in  a  small  quantity  of  water  and  add  to  the  lime  mix¬ 
ture.  Agitate  thoroughly  before  applying. 

Self -boiled  lime-sulphur  mixture.  The  8-8-50  self-boiled  lime-sulphur 
mixture  is  composed  of  8  pounds  of  good  stone  lime,  8  pounds  of  sulphur 


Plum  Cukculio  on  Peaches 


21 


and  50  gallons  of  water.  Any  finely  powdered  sulphur  (flowers,  flour, 
01  commercial  ground  sulphur)  may  be  used  in  the  mixture.  The 
formula  may  be  raised  to  16-16-100,  or  32-32-200  to  meet  the  capacity 
requirement  of  the  spray  tank.  The  amounts  used  in  the  following 
directions  are  for  a  200  gallon  tank. 

Place  32  pounds  of  lime  m  a  50  gallon  barrel  and  pour  on  enough 
water  to  start  slaking.  As  soon  as  the  lime  begins  to  slake,  32  pounds 
of  sulphur  should  be  added,  the  lumps  of  sulphur  if  present  having 
been  previously  broken  up.  Add  water  from  time  to  time  to  keep  the 
mixture  from  becoming  dry,  but  be  careful  not  to  drown  the  lime,  as 
this  will  cause  the  mixture  to  cease  boiling.  The  mixture  should  be 
stirred  constantly.  After  the  mixture  has  boiled  about  five  minutes, 
cool  with  water  to  prevent  further  cooking.  The  mixture  is  then  ready 
to  be  strained  into  the  spray  tank  and  diluted  to  200  gallons.  Precau¬ 
tions  should  be  taken  to  cool  the  mixture  with  water  before  the  red 
streaks  appear  to  any  extent  in  the  mixture;  on  the  other  hand  the 
mixture  must  not  be  cooled  before  the  boiling  has  progressed  sufficiently. 

The  required  amount  of  arsenate  of  lead  should  be  mixed  separately 
in  a  small  quantity  of  water,  and  this  mixture  then  added  to  the  self- 
boiled  lime-sulphur  mixture  in  the  spray  tank,  when  a  poison  is  called 
for  in  connection  with  the  self-boiled  solution. 

Thoroughness  and  Timeliness  in  Application 

The  fully  desired  results  from  dusting  or  spraying  will  not  be  ob¬ 
tained  unless  the  applications  are  made  in  a  thorough  manner  and  at 
the  proper  time.  This  is  true  in  the  control  of  most  insects  and  di¬ 
seases,  and  especially  is  it  true  of  curculio  control. 

In  spraying  a  tree,  the  operator  should  start  on  the  side  of  the  tree 
away  from  the  spray  machine  and  work  around  the  tree,  being  careful 
to  cover  the  tree  and  particularly  the  fruit  entirely.  The  hauling  of 
water  to  the  spray  outfits  in  the  orchard  will  very  often  facilitate  spray¬ 
ing.  Competent  supervision  of  spraying  is  essential  to  see  that  the 
mixtures  are  properly  prepared  and  thoroughly  applied. 

In  dusting,  the  machine  should  be  driven  down  each  tree  row  so  that 
the  operator  can  dust  the  near  side  of  each  tree.  Unsatisfactory  results 
are  usually  obtained  when  an  effort  is  made  to  dust  two  or  three  rows 
at  the  same  time.  Many  local  conditions  at  th§  time  of  dusting  will 
govern  the  exact  methods  to  be  employed,  but  one  should  aim  to  coat 
the  tree  lightly  and  envelop  it  in  a  cloud  of  dust. 

Picking  Up  Dropped  Fruit 

We  have  previously  shown  that  many  larvae  develop  in  the  small 
drops  in  spring,  and  that  these  larvae  transform  to  beetles  in  the  ground 
which  lay  eggs  in  the  late  varieties  of  peaches.  This  biological  habit 
suggests  the  importance  of  picking  up  all  dropped  fruit,  and  particularly 


22 


The  Bulletin,  March,  1923 


the  small  drops  found  under  the  trees  during  the  latter  part  of  April 
and  the  entire  month  of  May. 

It  is  especially  important  to  pick  up  the  very  small  drops  during 
late  April  and  early  May.  Moreover,  the  drops  should  be  picked  up 
at  least  three  times  every  two  weeks,  and  preferably  twice  each  week. 
The  necessity  for  picking  up  the  drops  frequently  and  regularly  is 
readily  understood  when  it  is  realized  that  many  of  the  larvae  do  not 
remain  in  the  drops  more  than  a  week  after  these  fruits  have  fallen. 
Some  of  the  infested  fruits  do  not  fall  until  after  the  larvae  are  half 
grown ;  in  fact  in  a  few  instances  we  have  seen  small  fruits,  from  which 
the  larvae  had  emerged,  still  hanging  on  the  tree. 

Cultivation  of  the  orchard  in  connection  with  the  picking  up  of  drops 
is  important.  Picking  up  of  drops  should  always  immediately  precede 
cultivation,  so  that  none  of  the  drops  will  be  covered  with  soil.  Results 
will  certainly  be  unsatisfactory  if  the  orchardist  does  not  give  due  at¬ 
tention  to  the  relation  of  the  picking  up  of  drops  and  cultivation.  This 
phase  of  curculio  control  together  with  the  timeliness  and  thorough¬ 
ness  of  picking  up  all  dropped  fruit,  both  large  and  small,  at  the  times 
indicated,  again  suggests  the  need  of  good  supervision  in  curculio  con¬ 
trol  operations. 

It  is,  of  course,  necessary  to  dispose  of  all  dropps  immediately  after 
they  have  been  gathered.  The  best  way  to  dispose  of  the  drops  is  to 
bury  them  with  'quicklime  in  a  pit  so  that  the  top  layer  will  be  two 
feet  below  the  surface  of  the  soil.  Boiling  the  drops  may  be  satisfac¬ 
tory  hut  caution  is  urged  not  to  allow  the  drops  to  stand  around  in 
containers  so  that  the  larvae  can  escape  to  the  ground  before  the  drops 
can  be  poured  into  the  boiling  water. 

The  cost  of  picking  up  of  drops  is  comparatively  small  when  the 
benefits  to  be  derived  are  considered.  This  control  operation  not  only 
reduces  the  number  of  curculios  but  in  certain  seasons  the  amount  of 
drown  rot  as  well. 

Orchard  Cultivation  and  the  Destruction  of  the  Curculio 

It  is  the  present  practice  of  fruit  growers  in  the  sandhill  section  to 
cultivate  frequently  throughout  the  season.  This  orchard  operation 
not  only  benefits  the  trees  hut  is  believed  by  the  growers  to  destroy  the 
larvae  and  pupae  of  the  curculio  while  in  their  cells  in  the  ground. 
Our  observations  indicate  that  comparatively  few  larvae  and  pupae  of 
the  curculio  are  destroyed  by  cultivation  in  the  sandy  type  of  soil  char¬ 
acteristic  of  this  sandhill  section;  at  least  the  number  killed  by  cultiva¬ 
tion  is  considerably  smaller  than  is  generally  supposed  by  fruit  growers. 
The  senior  writer  has  frequently  disturbed  larvae  and  pupae  of  the 
curculio  in  cages  in  the  insectary  and  observed  that  a  higher  percentage 
matured  than  would  ordinarily  be  expected  in  the  case  of  a  soft  bodied 
insect  like  the  immature  stages  of  the  curculio. 


Plum  Curculio  on  Peaches 


23 


During  the  months  of  May,  July  and  the  first  half  of  August,  when 
the  larvae  and  pupae  of  the  curculio  are  found  in  the  soil  in  numbers, 
cultivation  of  the  soil  will  probably  be  of  some  assistance  in  controll¬ 
ing  the  curculio.  It  would  seem,  however,  that  we  could  not  recommend 
a  cultivation  of  the  orchard  solely  for  the  purpose  of  destroying  larvae 
and  pupae  of  the  curculio. 


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